Composite knockdown pump

ABSTRACT

A CENTRIFUGAL FLUID PUMP SUITABLE FOR ASSEMBLY INTO AN OPERABLE UNIT WITHIN A CONFINED SPACE INCLUDING A PLURALITY OF IMPELLERS EACH MOUNTED WITHIN RESPECTIVE FLUID DISCHARGE MEMBERS AND IN RESPECTIVE ASSOCIATION WITH A PLURALITY OF FLUID SUCTION INLET MEMBERS, SUCH IMPELLERS BEING MOUNTED ON A COMPOSITE DRIVE SHAFT HAVING A PLURALITY OF MEMBERS INTEGRALLY ASSEMBLED TO PROVIDE A HIGH DEGREE OF RADIAL AND AXIAL ALIGNMENT AND A HIGH TORQUE TRANSFER CAPABILITY.

June 20, 1972 R. E. BALL COMPOSITE KNOCKDOWN PUMP 3 Sheets-Sheet 1 FiledFeb. 2, 1971 INVENTOR BOWL/4ND 6. 5/444 BY M June 20, 1972 R. E. BALL3,671,138

COMPOSITE KNOCKDOWN PUMP Filed Feb. 2, 1971 s Sheets-Sheet 2 INVENTOREOWA/VD 6. 5/1

June 20, 1972 5, BALL 3,671,138

COMPOSITE xnocxnown PUMP Filed Feb. 2, 1971 3 Sheets-Shoot 5 Bra 5.

INVENTOR EOWA/VD 6. 5AM,

United States Patent O 3,671,138 COMPOSITE KNOCKDOWN PUMP Rowland E.Ball, Long Beach, Calif assignor to Borg- Warner Corporation, Chicago,Ill. Filed Feb. 2, 1971, Ser. No. 111,962 Int. Cl. F0111 11/00 US. Cl.415111 21 Claims ABSTRACT OF THE DISCLOSURE A centrifugal fluid pumpsuitable for assembly into an operable unit within a confined spaceincluding a plurality of impellers each mounted within respective fluiddischarge members and in respective association with a plurality offluid suction inlet members; such impellers being mounted on a compositedrive shaft having a plurality of members integrally assembled toprovide a high degree of radial and axial alignment and a high torquetransfer capability.

BACKGROUND OF THE INVENTION This invention generally pertains to acentrifugal pump which may be readily assembled into operative conditionwithin a confined space with previously fitted and balanced componentsand also under conditions where the individual components andsubassemblies must pass through confined passageways to the space wherethe pump is assembled. An exemplary application for such a pump would beits service as a water jet propelling unit when installed in theconfined propulsion room of a marine vessel or boat having smallhatchways through one or more decks. The pump components andsubassernblies would need be transferred through such small hatchwaysfor assembly and also for subsequent disassembly and replacement. Someof the features and techniques relating to the embodiment disclosedherein have been previously developed as will become apparent fromreview of the description and drawing.

SUMMARY OF THE INVENTION An object of this invention is to provide aknockdown centrifugal pump having previously fitted and/or balancedcomponents which may be transferred through a small passage andassembled in a confined space.

Another object of this invention is to provide a pump having readilyinterchangeable replacement components.

A further object of this invention is to provide a pump having animproved weight to capacity ratio.

The foregoing and other objects and advantages are attained in aknockdown centrifugal pump having a plurality of impellers mounted on acomposite rotary drive shaft with each of the impellers being mountedwithin a respective circular fluid discharge housing and mounted influid communication with a respective circular fluid suction housing andthe drive shaft having a knockdown connection means for supporting saidshaft in radial and axial alignment. The connection means includes twotubular sections of the shaft with each section being provided withteeth radially defined in an annular area about one end thereof whichare provided to mesh together and support the shaft sections inalignment. A support mandrel is mounted within the shaft sections andconnected to connected to one of the shaft sections with tensioningmeans removably connected to the mandrel and to the other of the shaftsections for stressing the mandrel in tension between the shaft sectionsand thereby drawing the teeth into forcible engagement. Adjustableretaining means is connected to the mandrel and to the other of theshaft sections for retaining the mandrel in tension and the teeth inaligning engagement.

f 3,671,138 Ce Patented June 20, 1972 BRIEF DESCRIPTION OF THE DRAWINGIn the drawing:

FIG. 1 is a longitudinal sectional view of a centrifugal pump embodyingthe invention.

FIG. 2 is a transverse sectional view of the centrifugal pump takenalong the line 22 of FIG. 1.

FIG. 3 is an enlarged sectional view of the center shaft bearing andshaft connection shown in FIG. 1.

FIG. 4 is a stepped transverse sectional view taken along the line 44 ofFIG. 3.

FIG. 5 is an enlarged view of the coupling teeth from the outsidediameter of the shaft connection shown in FIGS. 1 and 3.

FIGS. 6 and 7 are enlarged views showing the development of the meshingcoupling teeth of the shaft connection shown in FIGS. 3 and 4.

FIG. 8 is an enlarged sectional view of hydraulic tensioning apparatusshown at the left of FIG. 1.

FIG. 9 is a transverse sectional view taken along the line 9-9 of FIG.8.

DESCRIPTION OF THE PREFERRED EMBODIMENT r Referring to FIG. 1 a pumpassembly 10 is shown having a composite housing 12. Fluid dischargehousings 14 and 16 are mounted along the axis of housing 12 on eitherside of a common center suction housing 18. A suction housing 20 isaxially mounted with discharge housing 14 at the left (driven) end ofthe pump and a suction housing 22 is axially mounted with dischargehousing 16 at the right end of the pump. The respective suction anddischarge housings are appropriately machined for assembly into properalignment when assembled as shown and are connected in sealed relationto form composite housing 12 by means of fasteners 24, such as capscrews or studs and nuts, for example.

As shown in FIGS. 1 and 2, discharge housings 14 and 16 are volute inconfiguration and each housing is equipped with an arcuately disposedrib 26 which has the dual purpose of directing the fluid discharge fromsuch housing and also of providing additional strength and rigidity tosuch housing. The volutes of housing 14 and 16 terminate in fluidoutlets 28. In the embodiment shown, the fluid outlet for housing 16terminates at a different tangential angle than for housing 14 and thusdoes not show in the drawing since its provision will become apparentfor a particular installation. Housings 18, 20 and 22 as shown providerespective fluid suction inlets 30 on each side of discharge housings 14and 16. Each of the housings are provided with axially disposed radialvanes 32 to prevent swirling of fluids entering inlets 30. The positionsof vanes 32 as shown are exemplary and may be rotated as required. It isto be noted that the flow direction of each of fluid outlets 28 and flowinlets 30 may be provided as necessary to properly connect pump assembly10 into a particular installation.

As shown in FIG. 1, left suction housing 20- is equipped with a ballbearing assembly 34 and a fluid seal assembly 36. Right suction housing22 is likewise equipped with a roller bearing assembly 38 and a fluidseal assembly 40. A composite impeller drive shaft 42, later described,is supported in axial and rotatable relation within housing 12 bybearing assemblies 34 and 38 in a well known manner. Seal assemblies 36and 40 provide a fluid seal around drive shaft 42 between the interiorand the exterior of housing 12. 7

As shown in FIGS. 1 and 3, center suction housing 18 is equipped with acomposite sleeve bearing assembly 44 which serves to provideintermediate rotatable support for drive shaft 42. Bearing assembly 44may be retained in suction housing 18 by a retainer key and ringarrangement 46, as shown, or by equivalent means. Sleeve bearing may befabricated rubber sleeve encircled by a plastic and layer wound glasslaminate, as shown, and will be lubricated by pumped fluids withinsuction housing 18. Bearing assembly 44 may be substituted by otherbearing embodiments for use with different kinds of pumped fluids, asmay be required.

As shown in FIGS. 1 and 2, a fluid impeller structure 48 is mounted ondrive shaft 42 and longitudinally disposed in fluid discharge alignmentwithin discharge housing 14. Cylindrical extensions formed on each ofimpeller 48 are disposed in accommodating recesses defined in suctionhousings 1 8 and 20. As shown, impeller 48 and housings 18 and 20 areequipped with complementary labyrinth fluid flow restriction structures50 which purpose are to restrict fluid flow from within the dischargehousing back into the suction housing. Such labyrinth flow restrictionstructures are well developed and will not be described further herein.

Impeller 48 and impeller 52, later mentioned, are of generallyconventional design and like elements bear the same numbers in thedrawing. Impeller 52 is mounted on drive shaft 42 within dischargehousing 16 as previously described for the mounting of impeller 48within discharge housing 14. Flow restriction structures 50 are alsoprovided with impeller 52 as shown. Impellers 48 and 52 are mounted inabutment against annular shoulders provided in drive shaft 42 and arefixed against rotation on the shaft by keys 60 fitted within slotsbetween the shaft and impellers. Impellers 48 and 52 each include a hub54 having a plurality of curved vanes 56 enclosed 'by shrouds 58 and 59.Shrouds 58 and 59 are formed to define fluid outlets into dischargehousings 14 and 16 and to define fluid inlets from the housings 18, 20and 22 as shown.

The pump assembly 10 depicted in FIG. 1 is shown in general proportionbut not to finite scale. As exemplary dimensions to give additionalperspective for pumps embodying the present invention, shaft 42 may beabout 80 inches (2.03 meters) in total length and about 6 inches (152.4millimeters) in outside diameter at bearing assembly 44. Also, such apump may be provided to utilize up to about 4,500 horsepower whenrotated up to about 1450 volutions per minute and when pumping at a loWdischarge head.

Referring now to FIGS. 1 and 3, composite drive shaft 42 is shown toinclude a first (left) tubular shaft section 62, a second (right) shaftsection 64. A retaining mandrel '66 is threadedly secured into one endof shaft section 64 and extends through shaft section 62 to be securedinto position as shown by a retaining spanner nut 68 threadedlyconnected to mandrel 6 6 and abutting shaft 62 within a shouldercounterbore provided in shaft section 62. A mandrel tensioning device70, later described, is removably attached to shaft section 62 and tomandrel 66.

Shaft section 62 and shaft section 64 are joined in axial and radialalignment by provision of a connection or coupling arrangement 72, shownin FIGS. 1 and 3-5. Teeth 74 and 74' are developed in generally radialdisposition in the annular faces of shaft sections 62 and 64.

The development of teeth 74 and 74 must be appropriate to providemeshing with the shaft sections in alignment. The preferred toothprofile and configuration is later described but splines or other toothprofiles, such as rectangular or triangular, may be provided with somemeasure of success, depending on the size of the shaft 42, therotational speed of the shaft and the amount of lateral and torqueloading on the shaft.

Couplings or connections such as shown inFIGS. 3-7 and referred toherein as a curvate coupling have been well developed to meet the needfor couplings requiring extreme accuracy and maximum load capacity, Thecurvate design provides an accurate, light, compact, and selfcontainedconnection in which the teeth 74 and 74 both serve to center and drive,as compared to other designs where the teeth drive only, and other meansof centering are necessary. The curvate coupling 72 has curved radialteeth 74 and 74 of constant depth, which are cut and ground into theannular face of each shaft section. These teeth may be produced with awide range of pressure angles and chamfered engaging surfaces. Thecurvate coupling 72 is a precision face spline for joining shaftsections 62 and 64 to form a single operating unit. This coupling hasthe advantages of accurate alignment, precision centering and positivedrive.

The curvature of curvate teeth 74 and 74' (see FIGS. 6 and 7) existsbecause the members are ground with a cup-type grinding wheel (notshown). One member may be made with the outside edge 76 of a wheel, asshown in FIG. 7, to form a concave or hourglass-shaped tooth. The matingmember shown in FIG. 6 may be made with the inside edge 78, thusproducing a convex or barrel-shaped tooth. The radius of the cuttingsurface is selected to give the desired length of tooth contact.

In contrast with other types of couplings, the curvate couplings 72 hasteeth 74 and 74 spaced continuously about the entire circumference, eachtooth tapering toward the center. Any attempt therefore to move onetooth out of position is resisted by all the other teeth in thecoupling. The controlled matching of the curved teeth in such a couplingis also an important factor in resisting movement and in centering shaftsections 62 and 64.

This centering action is of prime importance in maintaining the balanceof the pump impeller assembly. Much of the success of such a curvatecoupling design resides in the ability of the composite impellerassembly to re main in balance under continuous operation. Furthermore,the impeller assembly can be disassembled and then reassembled with thesame teeth mating without disturbing the original accuracy and balance.The interchangeability of ground curvate couplings simplifiesreplacement of worn or damaged impeller assemblies.

An enlarged view of the ground curvate coupling teeth at the outsidediameter is shown in FIG. 5. A chamfer 80 on the top of the teeth isautomatically ground as the tooth slot is being ground. This permits alarger fillet radius -82 to be used, thus strengthening the teeth. Alsoshown is a characteristic gable bottom 84 which eliminates anypossibility of forming a stress-raising step in the root of the tooth.

Another design feature of such curvate couplings permits localization ofthe tooth contact area. The tooth contact for most applications shouldbe centrally located and the length of contact should be approximately50% of the face width when meshed with the mating control coupling underlight stress. Under increased stress imposed by mandrel 66 the toothbearing area will increase, thus insuring a uniform distribution ofcontact over the entire tooth surface. The tension in the mandrel 66-must be suflicient to keep the coupling teeth in full engagement underall conditions of operation. a

In selecting the required coupling size, three factors determine theload which the coupling teeth will carry. The teeth must (1) be strongenough so they will not shear, (2) have sufficient surface area topreventpitting, galling, and fretting, and (3) be machined from enoughmaterial to withstand tension across the root of the tooth space.

' The shear strength is dependent upon the cross-sectional area of allthe teeth. Since there is no backlash in a curvate coupling, the teeth74 and 74' are in intimate contact so that half of the metal isordinarily removed in both members, regardless of the number of teeth ortheir depth. With this condition, the torque load is carried over ashear area approximately half as large as in a one-piece hollow shaft.The allowable surface loading will depend on the contact area of thecoupling teeth.

Supplemental specific information concerning couplings such as describedis available from the Gleason Works, 100 University Ave., Rochester,N.Y., U.'S.A.

As seen in FIGS. 1 and 3, tensioning mandrel 66 is threaded at its leftend to accommodate threaded retainer nut 68 and also of suflicientoutside diameter near its left end to fit closely enough within theinside diameter of shaft section 62 to establish a fluid seal withprovision of sealing means such as the O-ring seal shown. The mandrel isthereon reduced in diameter to near coupling 72 in order to provide anappropriate cross-sectional area to permit a predetermined elasticstrain or stretch in the mandrel when placed in tension. The right endof mandrel 66 terminates in an enlarged sleeve 86 which fits closelywithin accommodating bores defined in shaft sections 62 and 64 at thejuncture of coupling 72. A fluid seal is established between sleeve 86and shaft sections 62 and 64, and between the interior and exterior ofthe shaft sections, by seal means such as O-rings 88. The end of sleeve86 terminates with machine threads which fit into accommodating threadsdefined in shaft section 64 to form a threaded connection 90 as shown.

It is noted that the close fit of sleeve 86 within the shaft sections asshown can and would necessarily be utilized to axially align the shaftsections with some types of coupling teeth or other types of connectionas previously mentioned. Such expedient could become undesirable orunsatisfactory under some service conditions such as the example givenherein. The curvate type coupling 72, as herein described, does not needsupport of sleeve 86 for alignment and thus the fit between the sleeveand the shaft sections should be close enough only to assist the sealingfunction of O-rings '88. As shown, counterbores are defined in shaftsections 62 and 64 within coupling 72 to provide clearance betweensleeve 86 and teeth 74 and 74 and thereby prevent possible interference.

Referring now to FIGS. 8 and 9, a hydraulic tensioning means or jack 70is shown in operative connection with shaft section 62 and tensioningmandrel 66. Jack 70 includes a cylindrical support cage 92 which isgenerally tubular in shape and provided with lateral access windows asshown. At its right end cage 92 is provided with female machine threadswhich are adapted to be 'fitted over accommodating threads provided onshaft section 62 to form a threaded connection 94. An annular pistonchamber housing 96 is nested into a counterbore defined in the other endof cage 92. Housing 96 includes a cylindrical outer wall 98 and acylindrical inner wall 100 joined by an annular wall 102 to form anannular piston chamber 104 in which is fitted a movable annular piston106. Piston 106 is equipped with a sleeve 108 which extends from theopen end of chamber 104. Piston 106 and sleeve 108 are urged to retractinto chamber 104 by a spring 110 disposed about the sleeve and retainedin compression by means of a threaded bushing 112 fitted into anaccommodating female thread in wall 98 to form a threaded connection114. A threaded lag bolt 116 abuts the free end of sleeve 108 andextends through inner wall 100 into a threaded connection 118 providedby an accommodating thread defined in the end of shaft section 62. Atypical spanner wrench 120 equipped with pins, as shown forillustration, may be inserted through the windows of cage 92 and thepins engaged into the spanner holes of retainer nut 68 to rotate the nuton mandrel 66. The outer wall 98 of housing 96 is equipped with ahydraulic pressure fitting 122 through which hydraulic fluid may beintroduced under pressure into chamber 104. Such fluid will tend todisplace piston 106 and sleeve 108 and thereby exert tension on bolt 166and mandrel 66 with respect to shaft section 62.

In assembly of composite shaft 42, mandrel 66 may be placed within shaftsection 62 and threaded into engagement with shaft section 64 before theteeth 74 and 74 are engaged to form coupling 72. Coupling 72 may next beengaged by retainer nut threaded onto mandrel 66 in hand tight relationby hand or with spanner wrench as desired. Tensioning jack 70 may thenbe installed and suflicient fluid under pressure is applied into chamber104 to establish the proper degree of tension in mandrel 66 to obtainproper engagement of teeth 74 and 74'. When the proper pressure isreached, as shown by a suitable pressure indicator, the retainer nut 68is further tightened with the spanner wrench 120. The jack 70 is thereonremoved. The composite shaft 42 is then functional as an integral unit.

It is of note that the shaft 42 may be assembled as described before orafter installation of impellers 48 and 52; the complete impellerassembly may then be dynamically balanced as may be required, and thebalanced unit may then be disassembled and later reassembled as pumpassembly 10 is being assembled with the resulting impeller assemblybeing maintained in balance.

While only one preferred embodiment has been shown and described herein,other embodiments and variations will become apparent to those skilledin the art, all of which are intended to be included in the spirit ofthe invention as herein set forth.

I claim:

1. A centrifugal pump comprising:

(a) a plurality of impellers mounted on a composite rotary drive shaft;

(b) each of said impellers being mounted within a respective circularfluid discharge housing and mounted in fluid communication with acircular fluid suction housing;

(c) said drive shaft having a knockdown connection means for supportingsaid shaft in radial and axial alignment;

(d) said connection means including two tubular shaft sections with eachof said shaft sections being provided with teeth radially defined in anannular area about one end thereof;

(c) said teeth being provided to mesh together in forcible engagementand thereby support said shaft sections in alignment;

(f) a support mandrel mounted Within said shaft sections and connectedto one of said shaft sections; and

(g) adjustable retaining means connected to said mandrel and to theother of said shaft sections for retaining said mandrel in tension andsaid teeth in forcible engagement.

2. The pump of claim 1 wherein at least one of said knockdown connectionmeans is provided in said drive shaft between said impellers.

3. The pump of claim 1 wherein sleeve bearing means adapted forlubrication by pumped fluids is mounted in said pump to support saidshaft between said impellers.

4. The pump of claim 1 wherein the teeth defined about said one of saidshaft sections are concave in profile as viewed from the axis thereofand the teeth defined about said other of said shaft sections are convexas viewed along the axis thereof.

5. The pump of claim 1 wherein a fluid suction housing is axiallymounted on each end of each said fluid discharge housing.

6. The pump of claim 1 including tensioning means removably connected tosaid mandrel and to said other of said shaft sections for stressing saidmandrel in tension and thereby drawing said teeth into forcibleengagement.

7. The pump of claim 6 wherein said tensioning means includes hydraulicactuating means.

8. The pump of claim 6 wherein said tensioning means comprises removablepiston and cylinder means adapted 7 to stress said mandrel means inresponse to hydraulic fluid under pressure.

9. The pump of claim 1 wherein each said suction housing includes aradially disposed baffle therein for pre venting swirling of pumpedfiuids about the axis of said drive shaft.

10. The pump of claim 1 wherein said teeth are provided of curvateconfiguration.

11. A centrifugal pump comprising:

(a) a plurality of impellers mounted on a composite rotary drive shaft;

(b) each of said impellers being mounted within a respective circularfluid discharge housing and mounted in fluid communication with acircular fluid suction housing;

(c) said drive shaft having a knockdown connection means between eachsaid impeller for supporting said shaft in radial and axial alignment;

((1) said connection means including two tubular shaft sections witheach of said shaft sections being provided with teeth radially definedin an annular area about one end thereof;

(c) said teeth provided to mesh together in forcible engagement andthereby support said shaft sections in alignment;

(f) a support mandrel mounted within said shaft sections and connectedto one of said shaft sections; and

(g) adjustable retaining means connected to said mandrel and to theother of said shaft sections for retaining said mandrel in tension andsaid teeth in forcible engagement.

12. The pump of claim 11 wherein sleeve bearing means adapted forlubrication by pumped fluids is mounted in said pump to support saidshaft between said impellers.

13. The pump of claim 12 wherein a fluid section housing is axiallymounted on each end of each said fluid discharge housing.

14. The pump of claim 13 wherein said teeth are pro vided of curvateconfiguration.

injection of 15. The pump of claim 13 wherein the teeth defined aboutsaid one of said shaft sections are concave in profile as viewedfrom theaxis thereof and the teeth defined about said other of said shaftsections are convex as viewed along the axis thereof.

16. The pump of claim 14 including tensioning means removably connectedto said mandrel and to said other of said shaft sections for stressingsaid mandrel in tension and thereby drawing said teeth into forcibleengagement.

17. The pump of claim 16 wherein said tensioning means includeshydraulic actuating means.

18. The pump of claim 16 wherein said tensioning means comprisesremovable piston and cylinder means adapted to stress said mandrel meansin response to injection of hydraulic fluid under pressure.

19. The pump of claim 13 wherein each said suction housing includes aradially disposed bafile therein for preventing swirling of pumpedfluids about the axis of said drive shaft.

20. The pump of claim 1 wherein said impellers are tightly fitted onsaid shaft.

21. The pump of claim 1 wherein said shaft and said impellers mountedthereon are provided in dynamically balanced condition.

References Cited UNITED STATES PATENTS I 1,287,367 12/1918 Loewenstein4l598 1,334,461 3/1920 Kerr 4l598 2,358,744 9/1944 Stepanoif 415-98 3,038,411 6/1962 Hornschuch 417-360 3,303,994 2/1967 Morooka 417--360 C. J.HUSAR, Primary Examiner U.S. Cl. X.R.

